See the link below for all the others who have similar problems.
http://www.google.com/search?hl=en&q=Vista+Parental+controls+Locks+out+administrator&btnG=Google+Search
In some of the cases, restarting into Safe Mode allowed the user to create a new password for their admin accounts.
Hope this helps.
grif
i recently added a user account and turned on parental controls. somehow in the mix both of my accounts switched to standard accounts. when i am prompted for an administrator password the box pops up and there is nowhere to type in anything and the "OK" button is not able to be clicked. i cant do anything because there is no way to make an account or modify the accounts without an administrator password. and now there isnt any admistrator account at all. i have no way to modify anything. help please its vista home basic.

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